Water base resin composition

ABSTRACT

The present invention provides an aqueous resin composition that can be utilized in a wide variety of fields including paints for vehicles, paints for cans, paints for the outer facings of buildings, adhesives, inks, impregnating agents for fibers and paper, and sealing agents and the like, wherein the aqueous resin composition comprises a polyester resin (A) having an acid value from 10 to 50 and a hydroxyl value from 20 to 150, a vinyl modified polyester resin (B) having an acid value from 20 to 100 and a hydroxyl value from 20 to 150, and a curing agent (C).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an aqueous resin composition that canbe utilized in a wide variety of fields including paints for vehicles,paints for cans, paints for the outer facings of buildings, adhesives,inks, impregnating agents for fibers and paper, and sealing agents andthe like.

This application is the U.S. National Stage of International ApplicationNo. PCT/JP03/07209, filed on Jun. 6, 2003, the content of which isincorporated herein by reference.

Priority is claimed on Japanese Patent Application No. 2002-172679,filed Jun. 13, 2002, the content of which is incorporated herein byreference.

2. Description of Related Art

In recent years, environmental protection measures have requiredreductions in the volatile matter such as solvents that is dischargedfrom paints, and the substitution of solvent based paints with waterbased paints is occurring in most fields.

For example, in the vehicle paint application field, large quantities ofsolvent based paints are used, and reducing the quantity of organicsolvents discharged from these paints is now a primary concern, and thereplacement of solvents based paints with water based paints is beinginvestigated for paints used in all of the paint application processes,including priming, intermediate coats, and top coats.

Of the above types of paint, paints used in the intermediate coating ofvehicles require high performance characteristics including resistanceto chipping (chipping: paint film damage caused by small stones and thelike flying off the road and striking the paint film), good adhesion topaint films such as the priming coating, good storage stability (pigmentdispersibility), solvent resistance, and a favorable externalappearance, and as a result, resin compositions comprising an organicsolvent based polyester resin and an amino resin curing agent as theprimary components have been used conventionally.

In recent years, aqueous coatings have started to be used in somevehicle intermediate coating materials, although an aqueous paint foruse as a vehicle intermediate coating that is able to provide a highlevel of performance for all of the above required characteristics isstill to be developed.

For example, aqueous intermediate coating materials comprising apolyester resin, a curing agent, and an amine salt of an organicsulfonic acid have been reported (for example, patent reference 1:Japanese Unexamined Patent Application, First Publication No. Hei11-76937), and the disclosed technique enables a reduction in thequantity of organic solvent discharged during the vehicle paintapplication process. However, these aqueous intermediate coatingmaterials display inadequate pigment dispersibility, and problems ariseduring storage, including coagulation or precipitation of the pigment.

Known techniques for resolving problems associated with the storagestability of the paint, arising from factors such as coagulation orprecipitation of the pigment, or separation and precipitation of theresin, typically involve improving the pigment dispersibility using apigment dispersing agent such as a surfactant or the like. However, inorder to achieve the desired effect using this technique, a significantquantity of the pigment dispersing agent must be used, and because thispigment dispersing agent remains in the final paint film, it has adeleterious effect on the physical properties of the paint film such asthe water resistance and the like, which presents a considerablepractical problem.

Furthermore, it has also been reported that a paint produced using apigment and a water dispersible alkyd resin composition, in which ahydrophobic alkyd resin having an acid value of no more than 5 and ahydroxyl value of 1 to 50, and a hydrophilic alkyd resin having an acidvalue of 10 to 20 and a hydroxyl value of no more than 5 are bondedtogether chemically, displays minimal variation in viscosity over time,and offers excellent storage stability (for example, patent reference 2:Japanese Unexamined Patent Application, First Publication No. Hei5-287184). However, these water dispersible alkyd resin compositionsdisplay a structural characteristic wherein the surface of the dispersedparticles within the aqueous medium are coated with the hydrophilicalkyd resin having a hydroxyl value of no more than 5, and thehydrophobic alkyd resin having a hydroxyl value of 1 to 50 existsinternally, inside the particles, in other words, a structure in whichhydroxyl groups are localized inside the particles, and consequently thecurability of the composition when an amino resin or the like is used asthe curing agent is poor, and the physical characteristics of the paintfilm, such as the solvent resistance, tend to be inferior.

Furthermore, it has also been reported that an aqueous resin compositioncomprising an aqueous alkyd resin produced by condensing a specificvinylated fatty acid with a polyol compound, and then performing aneutralization with a basic compound, displays excellent resin stabilityand paint stability, and also offers excellent overall storage stability(for example, patent reference 3: Japanese Unexamined PatentApplication, First Publication No. Hei 9-111184). However, if a waterbased paint that utilizes this type of aqueous resin composition is usedas the intermediate coating material for a vehicle, although the storagestability of the paint is excellent, the chipping resistance of theproduced paint film is unsatisfactory.

As described above, substituting conventional solvent based paints withwater based paints, while retaining a good balance between the typicallyrequired characteristics for a vehicle intermediate coating materialsuch as chipping resistance, and ensuring excellent pigmentdispersibility and storage stability is extremely difficult, and atpresent no such water based paint is available, although the need for awater based paint capable of satisfying the above requiredcharacteristics to a high level is growing rapidly stronger in themarketplace.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an aqueous paint thatis able to maintain the typically required characteristics for a vehicleintermediate coating material, such as chipping resistance, while alsoproviding excellent pigment dispersibility and storage stability.

As a result of investigations, the inventors of the present inventionwere faced with the problem that although aqueous paints using anaqueous resin composition comprising, as primary components, a polyesterresin that utilizes either an alicyclic acid or an aliphatic acid, and acuring agent display excellent chipping resistance of the produced paintfilm, viscosity variation of the aqueous resin composition and theaqueous paint is large, and the paints are also prone to separation andprecipitation of the resin. Furthermore, they also observed that inthose cases in which a polyester that utilizes an aromatic acid is used,although the viscosity variation problem of the aqueous resincomposition improves, the chipping resistance deteriorates.

As a result of further investigations aimed at resolving these problems,the inventors discovered that, against predictions, an aqueous resincomposition comprising, as the primary components, a polyester resinhaving a specific acid value and hydroxyl value, which uses essentiallyonly an alicyclic acid and an aromatic acid, and uses either noaliphatic acid or an extremely reduced quantity, and a curing agentdisplayed a further improvement in viscosity variation over the case inwhich only an aromatic acid is used, and furthermore also offeredexcellent storage stability with no problems of resin separation orprecipitation. Furthermore, the chipping resistance of a paint filmobtained from an aqueous paint produced using such an aqueous resincomposition was also extremely good.

However, an aqueous paint produced using such an aqueous resincomposition required a slight improvement in pigment dispersibility, ason occasion the pigment could coagulate or precipitate on storage overtime.

As a result of further intensive investigations, the inventorsdiscovered that by combining the aforementioned polyester resin thatuses essentially only an alicyclic acid and an aromatic acid, with avinyl modified polyester resin having a specific acid value and hydroxylvalue, and containing an aliphatic acid chain having a bonded vinylpolymer section comprising a specific quantity of a structural unitderived from a carboxyl group containing monomer, and a curing agent, anaqueous resin composition with excellent storage stability was produced,and furthermore an aqueous paint using such a composition offeredexcellent stability with no precipitation of the pigment, and moreover,the chipping resistance of the produced paint film was also excellent,and they were hence able to complete the present invention.

In other words, the present invention provides an aqueous resincomposition comprising a polyester resin (A) having an acid value withina range from 10 to 50 and a hydroxyl value within a range from 20 to150, a vinyl modified polyester resin (B) having an acid value within arange from 20 to 100 and a hydroxyl value within a range from 20 to 150,and a curing agent (C), wherein the polyester resin (A) comprisesstructural units derived from an aromatic acid and from an alicyclicacid, and the combined total of those structural units derived from thearomatic acid and the alicyclic acid accounts for at least 70 mol % ofall the structural units derived from polybasic acids in the polyesterresin (A), and the vinyl modified polyester resin (B) comprises analiphatic acid chain having a bonded vinyl polymer section, in whichfrom 15 to 45% by weight of the vinyl modified polyester resin (B) isthe vinyl polymer section, and from 10 to 50% by weight of the vinylpolymer section is structural units derived from an α,β-ethylene basedunsaturated monomer having a carboxyl group.

The vinyl modified polyester resin (B) can be produced by condensing avinyl modified fatty acid (D) having a vinyl polymer section comprisinga carboxyl group and an aryl group, and a polyester resin (E) containinghydroxyl groups. Furthermore, the molar ratio in the aforementionedpolyester resin (A), between the structural units derived from anaromatic acid, and the structural units derived from an alicyclic acid,is preferably within a range from 20/80 to 50/50.

In addition, the present invention also provides an aqueous paintcomprising an aforementioned aqueous resin composition.

According to the present invention, an aqueous paint with excellentstorage stability, which is capable of forming a paint film withexcellent chipping resistance and external appearance can be produced.

DETAILED DESCRIPTION OF THE INVENTION

As follows is a more specific description of the present invention.

An aqueous resin composition of the present invention comprises apolyester resin (A) having an acid value within a range from 10 to 50and a hydroxyl value within a range from 20 to 150, a vinyl modifiedpolyester resin (B) having an acid value within a range from 20 to 100and a hydroxyl value within a range from 20 to 150, and a curing agent(C), wherein these components are dispersed or dissolved in an aqueousmedium.

The polyester resin (A) used in the present invention can be produced byan esterification reaction using a polybasic acid and a polyalcohol asthe principal reactants. The polyester resin (A) has an acid valuewithin a range from 10 to 50 and a hydroxyl value within a range from 20to 150.

In addition, the polyester resin (A) comprises structural units derivedfrom an aromatic acid and from an alicyclic acid as the polybasic acid,and the combined total of those structural units derived from thearomatic acid and the alicyclic acid accounts for at least 70 mol %, andpreferably at least 90 mol %, and even more preferably 100 mol %, of allthe structural units derived from polybasic acids in the polyester resin(A). By ensuring a value within the above range, an aqueous resincomposition capable of providing an aqueous paint with both excellentchipping resistance and excellent storage stability can be obtained.

In the polyester resin (A), the molar ratio between those structuralunits derived from the aromatic acid, and those structural units derivedfrom the alicyclic acid is preferably within a range from 20/80 to70/30, and even more preferably from 20/80 to 50/50. By ensuring a ratiowithin this range, an aqueous paint with excellent pigmentdispersibility and excellent storage stability can be obtained.

Examples of aromatic acids that can be used during the production of thepolyester resin (A) include various aromatic acids, including phthalicacid (anhydride), isophthalic acid, terephthalic acid,p-tert-butylbenzoic acid, trimellitic acid (anhydride), pyromelliticacid (anhydride), tetrachlorophthalic acid (anhydride), and 5-sodiumsulfodimethyl isophthalate.

Furthermore, examples of the alicyclic acid include a variety ofalicyclic polycarboxylic acids such as 1,1-cyclohexanedicarboxylic acid,hexahydrophthalic acid (anhydride), 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid (anhydride),methylhexahydrophthalic acid (anhydride), Het acid (anhydride),5-norbornene-2,3-dicarboxylic acid (anhydride) (HIMIC acid; registeredtrademark of Hitachi Chemical Co., Ltd.), hydrogenated trimellitic acid(anhydride), and endo-methylenetetrahydrophthalic acid (anhydride); aswell as a variety of alicyclic monocarboxylic acids such as4-tert-butylcyclohexane monocarboxylic acid and hexahydrobenzoic acid.

Furthermore, during production of the polyester resin (A), in additionto the aromatic and alicyclic polybasic acids described above, knownaliphatic acids such as adipic acid, azelaic acid, sebacic acid, maleicacid (anhydride), fumaric acid, itaconic acid, octenoic acid, andisononanoic acid may also be added.

Furthermore, during production of the polyester resin (A), in additionto the above polybasic acids, oils or fatty acids obtained by hydrolysisof those oils may also be used and suitable examples include coconutoil, hydrogenated coconut oil, rice bran oil, tall oil, soybean oil,castor oil, dehydrated castor oil, as well as the fatty acids obtainedby hydrolysis of these oils. Furthermore, in addition to the above oils,“CARDURA E” (a glycidyl ester of a branched aliphatic monocarboxylicacid, manufactured by Shell International B.V.) can also be used.

As described above, aliphatic acids, oils, and fatty acids obtained byhydrolysis of such oils, can be used in addition to the aromatic acidand the alicyclic acid described above, although from the viewpoint ofachieving the objects of the present invention, including superiorstorage stability for the aqueous paint, the quantities of suchadditional components is preferably kept as small as possible.

Examples of the polyalcohols that can be used in the production of thepolyester resin (A) include ethylene glycol, propylene glycol,1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol,diethylene glycol, dipropylene glycol, neopentyl glycol, triethyleneglycol, cyclohexanedimethanol, hydrogenated bisphenol A, glycerin,trimethylolethane, trimethylolpropane, pentaerythritol,dipentaerythritol, and sorbitol.

The structure of the polyester resin (A) produced using the variouspolybasic acids and polyalcohols described above may be either a linearstructure or a branched structure.

There are no particular restrictions on the method used for producingthe polyester resin (A), provided the method effects an esterificationof the polybasic acid and the polyalcohol, and either molten methods orsolvent methods can be used.

A molten method refers to a method in which the polybasic acid and thepolyalcohol are heated to 150 to 250° C. in a nitrogen atmosphere, andan esterification is conducted while the produced water is sequentiallyremoved, thereby producing a solid polyester resin (A) having apredetermined hydroxyl value and acid value.

Furthermore, a solvent method refers to a method in which the polybasicacid and the polyalcohol are heated in a solvent such as xylene toeffect an esterification, and the solvent is then removed to yield asolid polyester resin (A).

The solvent may also utilize a hydrophilic organic solvent, as describedbelow. In such cases, by adding a basic compound described below toneutralize the reaction mixture following the esterification reaction,and then dispersing or dissolving this neutralized mixture in water, anaqueous solution or an aqueous dispersion of the polyester resin (A) canbe obtained.

Furthermore, during the aforementioned esterification reaction, a knowncatalyst can also be used to promote the reaction, and examples of sucha catalyst include dibutyltin oxide, antimony trioxide, zinc acetate,manganese acetate, cobalt acetate, calcium acetate, lead acetate,tetrabutyl titanate, and tetraisopropyl titanate.

The acid value of the thus obtained polyester resin (A) is within arange from 10 to 50, and preferably from 15 to 40, and the hydroxylvalue is within a range from 20 to 150, and preferably from 40 to 150.If this acid value is less than 10, then the conversion of the polyesterresin (A) to an aqueous system is unsatisfactory, whereas if thehydroxyl value is less than 20, the curability of the product paint filmis unsatisfactory. Furthermore, if the acid value exceeds 50 or thehydroxyl value exceeds 150, the water resistance and the durability ofthe product paint film deteriorate.

Furthermore, a urethane modified polyester resin can also be used as thepolyester resin (A). Examples include products resulting from thepolyaddition of a polyisocyanate such as tolylene diisocyanate,methylene bisphenylisocyanate, or a trimethylolpropane adduct ofhexamethylene diisocyanate (TMP modified HDI), following synthesis ofthe aforementioned polyester resin (A).

Furthermore, the weight average molecular weight of the aforementionedpolyester resin (A) is preferably within a range from 1000 to 20,000,and even more preferably from 1000 to 10,000. By using a polyester resin(A) having a weight average molecular weight that falls within thisrange, an aqueous paint with excellent curability that is capable offorming a paint film with excellent water resistance and smoothness canbe obtained.

As follows is a description of a vinyl modified polyester resin (B) usedin the present invention. The vinyl modified polyester resin (B) has anacid value within a range from 20 to 100 and a hydroxyl value within arange from 20 to 150, and comprises an aliphatic acid chain having abonded vinyl polymer section, wherein from 15 to 45% by weight of thevinyl modified polyester resin (B) is the vinyl polymer section, andfrom 10 to 50% by weight of the vinyl polymer section is comprised ofstructural units derived from an α,β-ethylene based unsaturated monomerhaving a carboxyl group.

The vinyl modified polyester resin (B) can be produced using a method inwhich a vinyl modified fatty acid having a vinyl polymer section, whichis produced by a radical polymerization of an α,β-ethylene basedunsaturated monomer having a carboxyl group and another copolymerizableα,β-ethylene based unsaturated monomer in the presence of an unsaturatedfatty acid, and a polyester resin (E) having hydroxyl groups describedbelow are subjected to a condensation.

Vinyl modified polyester resins (B) produced using a method in which avinyl modified fatty acid (D) having a vinyl polymer section containinga carboxyl group and an aryl group, as described below (hereafterreferred to as a vinyl modified fatty acid (D)), is used as theaforementioned vinyl modified fatty acid, and this vinyl modified fattyacid (D) and a polyester resin (E) containing hydroxyl groups aresubjected to a condensation, are particularly preferred as they enablethe provision of an aqueous resin composition and an aqueous paint withexcellent storage stability.

The aforementioned vinyl modified fatty acid (D) can be produced by, forexample, a radical polymerization of an α,β-ethylene based unsaturatedmonomer having a carboxyl group, an α,β-ethylene based unsaturatedmonomer having an aryl group, and another copolymerizable α,β-ethylenebased unsaturated monomer in the presence of an unsaturated fatty acid.

The carboxyl groups of the vinyl modified fatty acid (including thevinyl modified fatty acid (D); hereafter the term vinyl modified fattyacid also includes the subordinate concept of the vinyl modified fattyacid (D)) used in the production of the vinyl modified polyester resin(B) include both groups derived from unsaturated fatty acids, and groupsderived from α,β-ethylene based unsaturated monomers having carboxylgroups, and both these types of carboxyl groups can undergo acondensation reaction having the hydroxyl groups of the hydroxyl groupcontaining polyester resin (E), although use of a vinyl modifiedpolyester resin (B) obtained through a condensation reaction betweencarboxyl groups derived from an unsaturated fatty acid, and the hydroxylgroups of a hydroxyl group containing polyester resin (E) are preferredin terms of the storage stability of the aqueous resin composition andthe aqueous paint.

Examples of unsaturated fatty acids that can be used in the productionof the vinyl modified fatty acid include fatty acids derived from thevarious (semi) drying oils and non-drying oils such as tung oil, linseedoil, soybean oil, safflower oil, castor oil, dehydrated castor oil, ricebran oil, cotton seed oil, and coconut oil. These fatty acids can beused singularly, or in combinations of two or more different fattyacids.

The quantity used of the unsaturated fatty acid preferably accounts for20 to 70% by weight, and even more preferably from 30 to 60% by weight,of the total quantity of raw materials used in the production of thevinyl modified fatty acid. By using a vinyl modified fatty acid producedusing a quantity of unsaturated fatty acid within the above range, thedispersion stability of the vinyl modified polyester resin (B), thestorage stability of an aqueous paint of the present invention, and thepaint film characteristics such as the water resistance and thecorrosion resistance of a paint film produced using an aqueous paint ofthe present invention, can all be improved.

Furthermore, examples of carboxyl group containing α,β-ethylene basedunsaturated monomers that can be used in the production of the vinylmodified fatty acid include α,β-ethylene based unsaturatedmonocarboxylic acids such as acrylic acid, methacrylic acid, andcrotonic acid, α,β-ethylene based unsaturated dicarboxylic acids such asmaleic acid, fumaric acid and itaconic acid, as well as acid anhydridessuch as maleic anhydride and itaconic anhydride, and monoester compoundsof these anhydrides, and using at least one of the above compounds ispreferred, and from the viewpoint of ensuring favorable physicalproperties for the produced paint film, the use of methacrylic acid isparticularly preferred.

The quantity used of α,β-ethylene based unsaturated monomer containingthis carboxyl group must be set so that from 10 to 50% by weight of thevinyl polymer section within the produced vinyl modified polyester resin(B) is formed from structural units derived from α,β-ethylene basedunsaturated monomer containing the carboxyl group. By ensuring aquantity within this range, the stability of the aqueous dispersion oraqueous solution of the vinyl modified polyester resin (B), and thestability of an aqueous resin composition of the present invention canboth be improved, an aqueous paint according to the present inventionwith excellent storage stability can be produced, and a paint film thatis resistant to whitening, even following drying, can be obtained.

Examples of α,β-ethylene based unsaturated monomers having aryl groupsthat can be used in the production of the vinyl modified fatty acid (D)include styrene, and styrene derivatives having functional groups suchas alkyl groups at any of the positions of the styrene aromatic ring.Specific examples of these styrene derivatives includetert-butylstyrene, α-methylstyrene, and vinyltoluene.

There are no particular restrictions on the quantity used of theα,β-ethylene based unsaturated monomer having an aryl group, althoughthe quantity is preferably at least 20% by weight, and even morepreferably from 30 to 70% by weight, relative to the combined quantityof all of the α,β-ethylene based unsaturated monomers used in thepolymerization of the vinyl polymer section containing a carboxyl groupand an aryl group. By ensuring that the quantity of the α,β-ethylenebased unsaturated monomer having an aryl group falls within the aboverange, the stability of the aqueous dispersion or aqueous solution ofthe vinyl modified polyester resin (B) can be further improved, and anaqueous resin composition and an aqueous paint of the present inventionwith even more superior storage stability can be produced.

During the production of the vinyl modified fatty acid, othercopolymerizable α,β-ethylene based unsaturated monomers can also beused, in addition to the α,β-ethylene based unsaturated monomer having acarboxyl group and the α,β-ethylene based unsaturated monomer having anaryl group described above. These other copolymerizable α,β-ethylenebased unsaturated monomers are α,β-ethylene based unsaturated monomersthat differ from both the aforementioned α,β-ethylene based unsaturatedmonomers having a carboxyl group and the aforementioned α,β-ethylenebased unsaturated monomers having an aryl group, and specific examplesinclude alkyl esters of (meth)acrylic acid such as methyl(meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl(meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, andcyclohexyl (meth)acrylate.

Furthermore, hydroxyalkyl esters of (meth)acrylic acid such as2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate canalso be used as an aforementioned other copolymerizable α,β-ethylenebased unsaturated monomer, provided they are used within a range thatenables the objects of the present invention to be achieved, and withina range which will not cause gelling in the condensation reactionbetween the vinyl modified fatty acid (D) and the polyester resin (E)having hydroxyl groups.

In addition, α,β-ethylene based unsaturated monomers having a non-ionicsurfactant action such as methoxypolyethylene glycol mono(meth)acrylate,polyethylene glycol mono(meth)acrylate and propylene glycol polyethyleneglycol mono(meth)acrylate can also be used as an aforementioned othercopolymerizable α,β-ethylene based unsaturated monomer.

The vinyl modified fatty acid used in the production of the vinylmodified polyester resin (B) can be produced by solution polymerizationor bulk polymerization or the like.

In a solution polymerization method, for example, α,β-ethylene basedunsaturated monomers such as the aforementioned α,β-ethylene basedunsaturated monomer having a carboxyl group, and an unsaturated fattyacid are either added in a dropwise manner, intermittently orcontinuously, or added in a single batch, to an organic solvent, in thepresence of a polymerization initiator, under an atmosphere of an inertgas, and the reaction mixture is then maintained at a temperature ofapproximately 70 to 150° C. to yield the vinyl modified fatty acid.

The polymerization initiator may be added in advance to the organicsolvent, as in the description above, or may also be added during thedropwise addition of the various α,β-ethylene based unsaturated monomersand the unsaturated fatty acid.

Examples of organic solvents that can be used in this type of solutionpolymerization include aromatic solvents such as toluene and xylene,ketone based solvents such as methyl ethyl ketone and methyl isobutylketone, and ester based solvents such as ethyl acetate and butylacetate.

The organic solvents that can be used in the solution polymerizationshould either be used in small quantities, or in those cases in which asolvent removal process is used, an alcohol based solvent such asisopropanol or n-butanol, or a glycol ether based solvent such as ethylcellosolve or butyl cellosolve can be used in a quantity that does notimpair the condensation reaction between the vinyl modified fatty acidand the polyester resin (E) having hydroxyl groups.

Furthermore, examples of polymerization initiators that can be used in asolution polymerization include organic peroxides such as t-butylperoxybenzoate, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, andbenzoyl peroxide, and azo compounds such as 2,2′-azobisisobutyronitrile,and 2,2′-azobis-2-methylbutyronitrile, and the above organic peroxidesare particularly preferred.

Furthermore, in the production of a vinyl modified fatty acid using asolution polymerization method, chain transfer agents can also be usedif necessary, and examples of chain transfer agents includealkylmercaptans such as t-dodecylmercaptan, normal dodecylmercaptan andnormal octylmercaptan, or α-methylstyrene dimers.

Furthermore, in a bulk polymerization method, α,β-ethylene basedunsaturated monomers such as the aforementioned α,β-ethylene basedunsaturated monomer having a carboxyl group, and an unsaturated fattyacid are added in a single batch, or added in a dropwise manner,intermittently or continuously, without the use of an organic solvent,and are then heated and mixed to yield the vinyl modified fatty acid.

Furthermore, during this process, by conducting the bulk polymerizationof the α,β-ethylene based unsaturated monomers and the unsaturated fattyacid in the presence of a polyester resin (E) having hydroxyl groupssuch as those described below, a vinyl modified polyester resin (B) canbe produced directly.

Next is a description of the polyester resin (E) having hydroxyl groups,which is subjected to a condensation reaction with the aforementionedvinyl modified fatty acid. The polyester resin (E) having hydroxylgroups refers to those materials produced by a condensation reactionusing a polybasic acid and a polyalcohol as a primary reaction componentthat contain a hydroxyl group. Depending on the targeted application,this polyester resin (E) having hydroxyl groups may also have beensubjected to urethane modification or silicone modification.

The polybasic acid used in the production of the polyester resin (E)having hydroxyl groups is preferably a compound having 2 to 4 carboxylgroups per one molecule, and suitable examples include phthalic acid,isophthalic acid, terephthalic acid, succinic acid, maleic acid,itaconic acid, fumaric acid, tetrahydrophthalic acid, hexahydrophthalicacid, methyltetrahydrophthalic acid, adipic acid, sebacic acid, azelaicacid, HIMIC acid, trimellitic acid, methylcyclohexenetricarboxylic acid,and pyromellitic acid, as well as the anhydrides of these acids.

Furthermore, the polyalcohol used in the production of the polyesterresin (E) having hydroxyl groups is preferably a compound having 2 to 6hydroxyl groups per one molecule, and examples include ethylene glycol,propylene glycol, neopentyl glycol, butanediol, pentanediol,1,4-cyclohexanedimethanol, trimethylolethane, trimethylolpropane,glycerin, trisisocyanurate, and pentaerythritol.

Furthermore, during the production of the polyester resin (E) havinghydroxyl groups, in addition to the above polybasic acid, animal basedoils, plant based oils, fatty acids produced by hydrolysis of such oils,or “CARDURA E” (a glycidyl ester of a branched aliphatic monocarboxylicacid, manufactured by Shell International B.V.) can also be used ifnecessary, provided the objects of the present invention can still beachieved.

Examples of the aforementioned animal based oils, plant based oils, andfatty acids produced by hydrolysis of such oils include coconut oil,hydrogenated coconut oil, rice bran oil, tall oil, soybean oil, castoroil, dehydrated castor oil, as well as the fatty acids obtained byhydrolysis of these oils.

From the viewpoint of storage stability of the product aqueous paint,the quantity used of the above animal based oils, plant based oils, orfatty acids produced by hydrolysis of such oils is preferably no morethan 50% by weight of the polyester resin (E) having hydroxyl groups.

Furthermore, the structure of the polyester resin (E) having hydroxylgroups may be either a linear structure or a branched structure.

The polyester resin (E) having hydroxyl groups can be produced by acondensation reaction using a polybasic acid and a polyalcohol as theprimary reaction components, and the molten methods or solution methodsdescribed for the production of the polyester resin (A) can be applied,using conditions in which, for example, the polyalcohol is present inexcess relative to the polybasic acid.

Furthermore, in a similar manner to that described above, the polyesterresin (E) having hydroxyl groups may also use a urethane modifiedpolyester produced by the polyaddition of a polyisocyanate such astolylene diisocyanate, methylene bisphenylisocyanate, or in certaincases, a trimethylolpropane adduct of hexamethylene diisocyanate (TMPmodified HDI), following synthesis of the polyester having hydroxylgroups.

The polyester resin (E) having hydroxyl groups preferably has a hydroxylvalue within a range from 50 to 300, and even more preferably from 100to 250. Provided the hydroxyl value falls within this range, thecondensation reaction between the aforementioned vinyl modified fattyacid and the polyester resin (E) having hydroxyl groups proceedssmoothly, and a product paint film with excellent water resistance anddurability can be ensured.

The vinyl modified polyester resin (B) used in the present invention canbe produced by mixing, heating, and effecting a condensation reactionbetween the vinyl modified fatty acid and the polyester resin (E) havinghydroxyl groups, which are preferably mixed in a ratio within a rangefrom 20:80 to 70:30. During this process, an additional quantity of thepolybasic acids listed as being suitable for use in the production ofthe polyester resin (E) having hydroxyl groups may also be added.

There are no particular restrictions on the temperature of the abovecondensation reaction, although temperatures within a range from 170 to210° C. are preferred. From the viewpoint of the rate of reaction, thetemperature is preferably adjusted in accordance with the variety of theα,β-ethylene based unsaturated monomer containing carboxyl group.

The condensation reaction occurs between the hydroxyl groups of thepolyester resin (E) having hydroxyl groups, and the carboxyl groups ofthe vinyl modified fatty acid. The vinyl modified fatty acid containsboth carboxyl groups derived from the unsaturated fatty acid andcarboxyl groups derived from the vinyl polymer section, although ofthese, reacting the carboxyl groups derived from the unsaturated fattyacid with the hydroxyl groups of the polyester resin (E) having hydroxylgroups is preferred in terms of producing a superior level of waterdispersibility or water solubility for the product vinyl modifiedpolyester resin (B).

Cases in which the carboxyl groups derived from the vinyl polymersection are carboxyl groups derived from methacrylic acid areparticularly preferred, as the reactivity of these carboxyl groups issignificantly lower than the reactivity of the carboxyl groups derivedfrom the unsaturated fatty acid, and consequently the carboxyl groupsderived from the unsaturated fatty acid take part almost exclusively inthe condensation reaction.

Furthermore, the vinyl modified polyester resin (B) can also be producedby a different method to that described above, under the presence of thepolyester resin (E) having hydroxyl groups, adding a small quantity ofan organic solvent if necessary, adding and mixing the monomers such asthe aforementioned unsaturated fatty acid, and the α,β-ethylene basedunsaturated monomer having a carboxyl group, and then raising thetemperature to effect a condensation reaction.

Furthermore, the vinyl modified polyester resin (B) can also be producedby a method in which the polyester resin (E) having hydroxyl groups andthe unsaturated fatty acid are subjected to a condensation reaction toform a polyester resin, and monomers such as the aforementionedα,β-ethylene based unsaturated monomer having a carboxyl group are thenadded and mixed to effect a polyaddition.

In addition, the vinyl modified polyester resin (B) can also be producedby subjecting the polyester resin (E) having hydrodxyl groups and theunsaturated fatty acid to a condensation reaction to form a polyesterresin, and then effecting an addition reaction of a vinyl polymer with acarboxyl group to this polyester resin.

Thus the obtained vinyl modified polyester resin (B) preferably has anacid value within a range from 20 to 100, and even more preferably from20 to 50, and most preferably from 20 to 40. Furthermore, the vinylmodified polyester resin (B) preferably has a hydroxyl value within arange from 20 to 150, and even more preferably from 40 to 150.

Provided the acid value falls within the above range, the vinyl modifiedpolyester resin (B) can be adequately dispersed or dissolved in water,and the water resistance and the durability of the product paint film isgood. Furthermore, provided the hydroxyl value falls within the aboverange, a paint film with excellent water resistance, durability andcurability can be produced.

Furthermore, in a vinyl modified polyester resin (B) used in the presentinvention, from 15 to 45% by weight of the resin must be accounted forby the aforementioned vinyl polymer section. By ensuring that thisproportion falls within this range, the stability of the aqueousdispersion or aqueous solution of the vinyl modified polyester resin (B)can be further improved, enabling an even more superior level of storagestability for an aqueous resin composition and aqueous paint of thepresent invention.

Furthermore, the weight average molecular weight of the vinyl modifiedpolyester resin (B) is preferably within a range from 10,000 to 150,000,and even more preferably from 30,000 to 100,000.

Known methods can be used for dispersing or dissolving the polyesterresin (A) and the vinyl modified polyester resin (B) used in the presentinvention in water, although of such known methods, phase inversionemulsification methods are ideal.

An example of a method of dispersing or dissolving the polyester resin(A) in water using a phase inversion emulsification method involvesneutralizing the polyester resin (A) having a basic compound, and thenadding the resin to water and stirring, to effect dispersion ordissolution in the water.

Specifically, a basic compound, and where necessary a quantity of ahydrophilic organic solvent, are added to and mixed with a solidpolyester resin (A) obtained from an aforementioned molten method orsolution method, thereby neutralizing either a portion of, or all of,the acid groups within the polyester resin (A), and water is then addedand mixed to disperse or dissolve the polyester resin (A) in the water.

In such a case, there are no particular restrictions on the timing ofthe addition of the hydrophilic organic solvent and the basic compoundto the polyester resin (A), and the hydrophilic organic solvent and thebasic compound may be added separately, or a mixture of the hydrophilicorganic solvent and the basic compound may be added at a suitable time.

In order to efficiently neutralize the acid groups of the polyesterresin (A) and effect dispersion or dissolution in the water, a method inwhich the solid polyester resin (A) is first dissolved in thehydrophilic solvent, the basic compound is then added to neutralizeeither a portion of, or all of, the acid groups, and water is then addedto disperse or dissolve the polyester resin (A) in water is preferred.

An example of a method of dispersing or dissolving the vinyl modifiedpolyester resin (B) in water using a phase inversion emulsificationmethod involves neutralizing the vinyl modified polyester resin (B)having a basic compound, and then adding the resin to water andstirring, to effect dispersion or dissolution in the water.

Specifically, a basic compound, and where necessary a quantity of ahydrophilic organic solvent, are added to and mixed with a vinylmodified polyester resin (B), thereby neutralizing either a portion of,or all of, the acid groups within the vinyl modified polyester resin(B), and water is then added to disperse or dissolve the polyester resin(B) in the water.

In such a case, there are no particular restrictions on the timing ofthe addition of the hydrophilic organic solvent and the basic compoundto the vinyl modified polyester resin (B), and the hydrophilic organicsolvent and the basic compound may be added separately, or a mixture ofthe hydrophilic organic solvent and the basic compound may be added at asuitable time.

In order to efficiently neutralize the acid groups of the vinyl modifiedpolyester resin (B) and effect dispersion or dissolution in the water, amethod in which the vinyl modified polyester resin (B) is firstdissolved in the hydrophilic solvent, the basic compound is then addedto neutralize either a portion of, or all of, the acid groups, and wateris then added to disperse or dissolve the polyester resin (B) in wateris preferred.

Furthermore a basic compound, and where necessary a quantity of ahydrophilic organic solvent can also be added to a mixture of apolyester resin (A), a vinyl modified polyester resin (B), and a curingagent (C) described below, and water then added to disperse or dissolvethese components in water.

Examples of the hydrophilic solvent described above include etheralcohols such as monoether compounds of ethylene glycol, and methanol,ethanol, propanol or butanol; monoether compounds of propylene glycol,and methanol, ethanol, propanol or butanol; monoether compounds ofdiethylene glycol, and methanol, ethanol, propanol or butanol; monoethercompounds of dipropylene glycol, and methanol, ethanol, propanol orbutanol; as well as 1,3-butylene glycol-3-monomethyl ether (common name:3-methoxybutanol), 3-methyl-3-methoxybutanol (common name: solfit), andether esters such as methyl cellosolve acetate that display indefinitesolubility in water at 20° C. The quantity used of the hydrophilicorganic solvent can be set so as to ensure efficient neutralization ofthe acid groups of the polyester resin (A) and the vinyl modifiedpolyester resin (B), although from the viewpoint of a low VOC, thequantity of the solvent is preferably kept small.

Furthermore, the basic compound used for neutralizing either a portionof, or all of, the acid groups within the polyester resin (A) or thevinyl modified polyester resin (B) can utilize typical known compounds,and suitable examples include the hydroxides of alkali metals or alkaliearth metals such as sodium hydroxide, potassium hydroxide, lithiumhydroxide, calcium hydroxide, and barium hydroxide; primary monoaminessuch as ammonia, ethylamine, propylamine, butylamine, benzylamine,monoethanolamine, neopentanolamine, 2-aminopropanol, and3-aminopropanol; secondary monoamines such as diethylamine,diethanolamine, di-n- or iso-propanolamine, N-methylethanolamine, andN-ethylethanolamine; and tertiary monoamines such asdimethylethanolamine, trimethylamine, triethylamine,methyldiethanolamine, and dimethylaminoethanol; as well as polyaminessuch as diethylenetriamine, hydroxyethylaminoethylamine, andethylaminoethylamine; and moreover, suitable combinations of basiccompounds may also be used to adjust the hydrophilicity of theaforementioned polyester resin (A).

The quantity used of this basic compound is preferably within a rangefrom 40 to 100 mol %, and even more preferably from 60 to 100 mol %,relative to the quantity of carboxyl groups within the polyester resin(A) or the vinyl modified polyester resin (B).

There are no particular restrictions on the curing agent (C) used in thepresent invention, provided the agent displays reactivity towards thehydroxyl groups of the polyester resin (A) and the vinyl modifiedpolyester resin (B), and examples include amino resins and blockisocyanates.

Specific examples of these amino resins include methylolated aminoresins produced by the reaction of one or more materials such asmelamine, urea and benzoguanamine, with formaldehyde, and methylolatedamino resins containing imino group. Of these, resins particularlysuited to forming aqueous formulations are preferred, and specificexamples include resins in which either all, or a portion of, themethylol groups within the above amino resins have been etherified witha monovalent alcohol of 1 to 8 carbon atoms, such asbutoxymethylmelamine resin, methoxymethylated melamine resin, andmethoxy-butoxy mixed etherified methylmelamine resin.

Furthermore, examples of the aforementioned block isocyanates includeblock isocyanates produced by the blocking of an adduct of an organicdiisocyanate compound and a polyalcohol, a low molecular weightpolyester resin containing hydroxyl group, a low molecular weight alkydresin containing hydroxyl group or water, and a polymer produced fromthe types of organic diisocyanate compounds described above (includingisocyanurate type polyisocyanate compounds and uretodione compounds),using a known blocking agent such as an oxime, a phenol, an alcohol, ora diketone.

Examples of the aforementioned organic diisocyanate compounds includethe various cyclic diisocyanates (including alicyclic diisocyanates)such as xylylene diisocyanate or isophorone diisocyanate, the variousaromatic diisocyanates such as tolylene diisocyanate or4,4-diphenylmethane diisocyanate, and the various aliphaticdiisocyanates such as hexamethylene diisocyanate ortrimethylhexamethylene diisocyanate.

Of the above compounds, the use of materials in which one terminal ofthe isocyanate group is modified with a polyoxyethylene glycol or thelike, and the other terminal is blocked with an alkoxy group, or waterdispersible block isocyanates in which one terminal is modified with apolyoxyalkylene compound comprising a group having an active hydrogenatom is preferred.

An aqueous resin composition of the present invention can be produced bymixing an aqueous dispersion or aqueous solution of an aforementionedpolyester resin (A), an aqueous dispersion or aqueous solution of anaforementioned vinyl modified polyester resin (B), and a curing agent(C) using a known method.

Furthermore, the aqueous resin composition can also be produced bymixing the polyester resin (A), the vinyl modified polyester resin (B)and the curing agent (C), adding a hydrophilic organic solvent wherenecessary, adding and stirring a basic compound and/or an emulsifyingagent, and then adding water to either disperse or dissolve the mixture.

The relative contents of the polyester resin (A), the vinyl modifiedpolyester resin (B) and the curing agent (C) within the thus obtainedaqueous resin composition preferably result in a weight ratio [polyesterresin (A)+vinyl modified polyester resin (B)]/curing agent (C) thatfalls within a range from 50/50 to 90/10, and even more preferably from60/40 to 85/15.

Furthermore, the weight ratio [polyester resin (A)/vinyl modifiedpolyester resin (B)] is preferably within a range from 50/50 to 85/15.By adjusting the respective quantities to ensure ratios within the aboveranges, an aqueous paint with excellent adhesion, curability and storagestability can be produced, and a paint film with superior chippingresistance and water resistance can also be achieved.

As follows is a description of an aqueous paint of the presentinvention.

An aqueous paint of the present invention can be produced by forming anaqueous resin composition according to the present invention asdescribed above, adding curing catalysts, pigments, antifoaming agents,dispersants, surface regulating agents, color separation preventionagents, flow regulating agents, or other resins as required, and thenmixing the components using a conventional apparatus. Particularly inthose cases in which a pigment is used, the pigment must be mixed witheither the aqueous resin composition or the resin components that formthe aqueous resin composition, and then thoroughly dispersed using aconventional dispersing device.

The aforementioned curing catalysts are used to promote the curing ofthe aqueous resin composition or aqueous paint of the present invention,and examples include acid catalysts such as organic acids likeparatoluenesulfonic acid, dodecylbenzenesulfonic acid,dinonylnaphthalenedisulfonic acid, amine block compounds produced fromsuch acids, half esters of tetrachlorophthalic anhydride and amonovalent alcohol, and trichloroacetic acid; metal compounds such astetraisopropyl titanate, dibutyltin laurate, dibutyltin acetate,dibutyltin dioctoate, and cobalt naphthenate; and various phosphorusbased acidic compounds such as monoalkylphosphoric acids,dialkylphosphoric acids, monoalkylphosphorous acids dialkyl phosphorousacids.

The quantity used of such a curing catalyst is preferably within a rangefrom 0.1 to 10 parts by weight per 100 parts by weight of the combinedtotal of the polyester resin (A), the vinyl modified polyester resin (B)and the curing agent (C).

The pigments described above can utilize known pigments, and suitableexamples include carbon black, metal oxides such as titanium oxide,magnesium oxide, zinc oxide and iron oxide, inorganic pigments such asaluminum flakes, mica, silicates, strontium chromate, zinc chromate,barium sulfate and calcium carbonate, and organic pigments such asphthalocyanine blue, phthalocyanine green, quinacridone,benzimidazolone, threne and perylene, and these may be used eithersingularly, or in combinations of two or more different pigments.

Furthermore, examples of the aforementioned other resins includepolyether polyols, and low molecular weight polyester polyols havingsecondary alcohol based hydroxyl group formed from a polyol, a lactoneand an acid anhydride.

The viscosity of an aqueous paint of the present invention is preferablywithin a range from 20 to 80 seconds when measured at a temperature of20° C. using a Ford cup No. 4.

One example of a method of using an aqueous paint of the presentinvention to form a paint film with the desired high level of practicalproperties is a method in which an aqueous paint of the presentinvention is applied to the surface of a substrate that has beensubjected to a surface treatment, and where necessary coated with aprimer layer such as an electrodeposition film, and the applied paint isthen cured under heat.

Methods such as spray methods, electrostatic methods, andelectrodeposition methods can be used as the method of applying theaqueous paint of the present invention to the substrate surface, andapplication and curing should be conducted to produce a dried and curedpaint film of the desired thickness.

The conditions for the heat curing may be set appropriately to ensurethat the cross linking reaction between each of the resin components ofthe aqueous paint and the curing agent proceeds satisfactorily, forexample, a temperature of 110 to 170° C. for a period of 15 to 40minutes.

Furthermore, examples of substrates that can be coated with an aqueouspaint of the present invention include iron or non-iron metal basedmetallic materials or metal products such as steel plate, stainlesssteel plate, chromed or plated sheets, galvanized sheets, tin plate,aluminum plate, aluminum sashes and aluminum wheels, as well as timber,slate sheets, roof tiles, and glass.

Furthermore, an aqueous paint of the present invention is particularlysuitable for the intermediate coating of vehicles, and a layered paintfilm can be produced by applying a top coat to the surface of the paintfilm produced from the aqueous paint of the present invention. Acomposite paint film produced by applying a top coat to the surface ofthe intermediate coating has excellent external appearance, is unlikelyto undergo paint film separation, and displays excellent resistance tochipping.

EXAMPLES

As follows is a more specific description of the present invention usinga series of reference examples, examples and comparative examples.

Reference Examples 1 to 5 (Sample Preparations of Polyester Resins)

In a 3 liter 4 neck flask equipped with a stirrer, a thermometer, areflux condenser fitted with a water trap, and a nitrogen gas inlet wereplaced a raw material composition as shown in Table 1 and 0.5 parts byweight of dibutyltin oxide, the temperature was raised to 220° C., and adehydration condensation reaction was carried out. During the reaction,the acid value was measured by removing a portion of the resin solution,and the reaction was continued until the acid value of the solutionproduced by diluting this portion with butyl cellosolve until thenon-volatile portion reached 60% by weight reached the value shown inTable 1.

Following completion of the reaction, when the reaction mixture hadcooled to 150° C., where necessary a hydrophilic organic solvent shownin Table 1 was added and stirred for one hour, and subsequently, at 90°C., a basic compound shown in Table 1 was added and stirred at the sametemperature for one hour. Sufficient ion exchange water was then addedto reduce the non-volatile component to 40% by weight, thereby yieldingan aqueous dispersion of a polyester resin (A)−1 to 5. The properties ofeach resin dispersion are summarized in Table 1.

TABLE 1 Reference Example Units 1 2 3 4 5 Raw isophthalic acid parts 58123 302 317 materials terephthalic acid by phthalic anhydride weight 369HHPA 485 455 280 THPA 162 adipic acid 280 NPG 147 129 103 82 170 1,6HD168 209 233 309 193 TMP 142 84 82 78 40 Acid value of butyl cellosolve13.2 17.5 19 10.2 29.4 solution with non-volatile component of 60% byweight hydrophilic BCS parts 100 30 organic PnP by 50 50 solvent weightbasic triethylamine 29 41 compound DMEA 33 24 28 Properties Polyesterresin Hydroxyl value 142 75 50 98 35 Acid value of aqueous 7.5 12.3 11.46.2 22.3 dispersion Weight average molecular 3700 6400 12000 4200 5000weight Name (A)-1 (A)-2 (A)-3 (A)-4 (A)-5 HHPA: hexahydrophthalicanhydride THPA: tetrahydrophthalic anhydride NPG: neopentyl glycol1,6HD: 1,6-hexanediol TMP: trimethylolpropane BCS: ethyleneglycol-n-butyl ether PnP: propylene glycol-n-propyl ether DMEA:dimethylethanolamine

Reference Examples 6 to 9 (Sample Preparations of Polyester Resinshaving Hydroxyl Groups)

In a 3 liter 4 neck flask equipped with a stirrer, a thermometer, areflux condenser fitted with a water trap, and a nitrogen gas inlet wereplaced a raw material composition as shown in Table 2 and 0.5 parts byweight of dibutyltin oxide, the temperature was raised to 220° C., and adehydration condensation reaction was carried out. During the reaction,the acid value was measured by removing a portion of the resin solution,and the reaction was continued until the acid value of the solutionproduced by diluting this portion with butyl cellosolve until thenon-volatile portion reached 60% by weight reached the value shown inTable 2, thereby yielding a solid polyester resin having hydroxyl groups(E)−1 to 4 that functions as a raw material for a vinyl modifiedpolyester resin (B). The properties of each resin are summarized inTable 2.

TABLE 2 Reference Example 6 7 8 9 Raw isophthalic acid 161 277 190materials phthalic anhydride 395 (parts by adipic acid 330 39 244 42weight) coconut oil fatty acid 168 504 soybean oil fatty acid 53 NPG 10117 22 1,6HD 44 45 44 45 TMP 311 336 413 108 PE 110 Properties PolyesterHydroxyl value 192 165 236 90 resin Acid value 9.7 13.2 12 9.2 havingWeight average 9200 8900 10500 7500 hydroxyl molecular weight groupsName (E)-1 (E)-2 (E)-3 (E)-4 PE: pentaerythritol

Reference Examples 10 to 12 (Sample Preparations of Vinyl Modified FattyAcids)

In a 3 liter 4 neck flask equipped with a stirrer, a thermometer, areflux condenser, and a nitrogen gas inlet were placed the quantities offatty acids and xylene shown in Table 3, the temperature was raised to130° C. with constant stirring, and a mixture of a vinyl copolymerizablemonomer and a polymerization initiator was then added over a period of 3hours. Stirring was continued at 130° C. overnight, and followingsubsequent cooling to 80° C., a quantity of methyl ethyl ketone shown inTable 3 was added, yielding a vinyl modified fatty acid (D)−1 to 3 withthe properties shown in Table 3. The non-volatile component of thesolution was 50% by weight.

TABLE 3 Reference Example 10 11 12 Raw materials dehydrated castor oil356 fatty acid (parts by weight) castor oil fatty acid 356 tall oilfatty acid 73 linseed oil fatty acid 489 styrene 172 110 117 n-butylmethacrylate i-butyl methacrylate 257 417 2-ethylhexyl methacrylate 121methacrylic acid 215 117 200 Polymerization t-butylperoxy benzoate 30 3030 initiator (parts by weight) Organic solvent xylene 650 650 650 (partsby weight) methyl ethyl ketone 350 350 350 Vinyl modified fatty Acidvalue of solution 98 69 115 acid Weight average molecular 6400 7000 6500weight Name (D)-1 (D)-2 (D)-3

Reference Examples 13 to 16 (Sample Preparations of Vinyl ModifiedPolyester Resins)

In a 3 liter 4 neck flask equipped with a stirrer, a thermometer, areflux condenser fitted with a water trap, and a nitrogen gas inlet wasplaced a raw material composition shown in Table 4, the temperature wasgradually raised to 180° C., the xylene and methyl ethyl ketone wereboiled off and a dehydration condensation was carried out. The reactionwas continued until the acid value of the resin solution produced bydiluting the reaction mixture with butyl cellosolve until thenon-volatile portion reached 50% by weight reached the value shown inTable 4. Following completion of the reaction, when the reaction mixturehad cooled to 150° C., where necessary a hydrophilic organic solventshown in Table 4 was added and stirred for one hour, and subsequently,at 90° C., a basic compound shown in Table 4 was added and stirred atthe same temperature for one hour. Sufficient ion exchange water wasthen added to reduce the non-volatile component to 40% by weight,thereby yielding an aqueous dispersion of a vinyl modified polyesterresin (B)−1 to 4. The properties of each resin dispersion are summarizedin Table 4.

TABLE 4 Reference Example Units 13 14 15 16 Raw (E)-1 parts 760materials (E)-2 by 600 (E)-3 weight 500 (E)-4 650 (D)-1 240 (D)-2 500350 (D)-3 400 Acid value of butyl cellosolve 6.5 19.0 25.0 14.8 solutionwith non-volatile component of 50% by weight hydrophilic BCS parts 50 10organic PnP by 100 solvent weight basic triethylamine 48 23 104 compoundDMEA 23 Properties Vinyl modified Hydroxyl value 38 80 55 40 polyesterresin Acid value of aqueous dispersion 13.0 15.2 21.3 10.7 Weightaverage molecular weight 57000 100000 63000 51000 Name (B)-1 (B)-2 (B)-3(B)-4

Examples 1 to 5, Comparative Examples 1 to 3

In a stainless steel vessel were placed a predetermined quantity of avinyl modified polyester resin (B)−1 to 4, a predetermined quantity oftitanium oxide R-930 or titanium oxide CR-97, and an equal quantity ofglass beads as shown in Table 5, a quantity of an antifoaming agentBYK-080 equivalent to 0.5% by weight relative to the combined total ofthe vinyl modified polyester resin and the titanium oxide was added, andthe mixture was dispersed for two hours using a paint shaker.

Subsequently, predetermined quantities of a polyester resin (A)−1 to 5and a curing agent shown in Table 5 were added, the mixture was stirredfor 5 minutes, the glass beads were removed, and the viscosity wasadjusted by adding ion exchange water to produce a Ford cup No. 4viscosity of 50 seconds (20° C.), thereby yielding an aqueous painteach. The viscosity of each aqueous paint was measured immediatelyfollowing production, and then again after storage for 10 days at 40°C., and the variation in viscosity is shown in Table 6. Furthermore, thenon-volatile component of each aqueous paint is also shown in Table 6.

TABLE 5 Comparative Units Example No. Example No. (parts by weight) 1 23 4 5 1 2 3 Polyester resin (A)-1 123 140 (A)-2 75 150 (A)-3 150 (A)-4123 (A)-5 140 Vinyl modified polyester resin (B)-1 53 60 (B)-2 63 35(B)-3 75 150 (B)-4 53 Curing agent C-370 34 17 34 34 S-695 61 30 61 61Titanium oxide R-930 67 82 67 82 82 CR-97 67 67 82 C-370: Cymel C-370 (apartially etherified methylol melamine resin manufactured by MitsuiCytec Ltd., non-volatile component: 88% by weight) S-695: SUPERBECKAMINE S-695 (a melamine resin, manufactured by Dainippon Ink andChemicals Inc., non-volatile component: 66% by weight) BN-69: ELASTRONBN-69 (a water dispersed block isocyanate, manufactured by Dai-ichiKogyo Seiyaku Co., Ltd., non-volatile component: 40% by weight) R-930:TIPAQUE R-930 (titanium oxide, manufactured by Ishihara Sangyo Kaisha,Ltd.) CR-97: TIPAQUE CR-97 (titanium oxide, manufactured by IshiharaSangyo Kaisha, Ltd.)

Reference Example 21 (Preparation of an Intermediate Coated Sheet)

The aqueous paints obtained in the examples 1 to 5 and the comparativeexamples 1 to 3 were each sprayed onto an electrodeposition sheet(manufactured by Nippon Route Service Company Co., Ltd.) in sufficientquantity to generate a dried paint film with a thickness of approx 35μm, and the coating was then left to stand for 10 minutes at roomtemperature, and dried by heating for 10 minutes at 60° C. Subsequently,the coating was baked for 30 minutes at 140° C., yielding anintermediated coated sheet. Using these intermediate coated sheets, theintermediate coating performance tests shown in Table 6, namely, gloss,hardness and xylene rubbing tests were carried out.

Reference Example 22 (Preparation of a Base Coat Paint)

A mixture with the composition described below was diluted with adiluting solvent comprising a mixture of toluene and ethyl acetate in aweight ratio of 9/1, until the viscosity using a Ford cup No. 4 was from12 to 13 seconds, thereby yielding a base coat paint.

-   ACRYDIC A-322 (an acrylic resin, manufactured by Dainippon Ink and    Chemicals Inc.); 160 parts by weight-   SUPER BECKAMINE L-117-60 (a butylated melamine resin, manufactured    by Dainippon Ink and Chemicals Inc.); 33 parts by weight-   ALPASTE 1860YL (an aluminum paste, manufactured by Toyo Aluminum    Co., K. K.); 23 parts by weight-   FASTOGEN Blue NK (a phthalocyanine based organic pigment,    manufactured by Dainippon Ink and Chemicals Inc.); 2 parts by weight

Reference Example 23 Preparation of a Clear Coat Paint

A mixture with the composition described below was diluted with adiluting solvent comprising a mixture of xylene and 1-butanol in aweight ratio of 8/2, until the viscosity using a Ford cup No. 4 was from22 to 24 seconds, thereby yielding a clear coat paint.

-   ACRYDIC A-345 (an acrylic resin, manufactured by Dainippon Ink and    Chemicals Inc.); 127 parts by weight-   SUPER BECKAMINE L-117-60 (a butylated melamine resin, manufactured    by Dainippon Ink and Chemicals Inc.); 50 parts by weight-   TINUVIN 900 (a benzotriazole based ultraviolet absorption agent,    manufactured by Ciba-Geigy Co., Ltd.); 3 parts by weight-   SANOL LS-765 (a hindered amine based light stabilizer, manufactured    by Sankyo Co., Ltd.); 1 part by weight-   KP-321 (a leveling agent, manufactured by Shin-Etsu Chemical Ltd.);    0.05 parts by weight

Reference Example 24 Preparation and Evaluation of Top Coated Sheets

The base coat paint prepared in the reference example 22 was sprayedonto each of the intermediate coated sheets produced in the referenceexample 21 in sufficient quantity to generate a dried paint film with athickness of approx 15 μm, the coating was left to stand for 3 minutesat room temperature, and the clear coat paint prepared in the referenceexample 23 was then sprayed onto each sheet in sufficient quantity togenerate a dried paint film with a thickness of approx 35 μm. Each sheetwas subsequently left to stand for 10 minutes at room temperature, andwas then baked for 30 minutes at 140° C. to produce a top coated sheetwith a composite paint film.

Visual examination of the external appearance of each top coated sheetshowed that all of the top coated sheets displayed a superior appearancewith no problems such as gloss deterioration or the like. Furthermore,when chipping resistance tests were conducted using the top coatedsheets, each top coated sheet displayed excellent resistance tochipping. The results are shown in Table 6.

TABLE 6 Comparative Example No. Example No. 1 2 3 4 5 1 2 3 Viscosityvariation of −3 0 0 +3 −6 +20 *precip- +3 aqueous paint (seconds) ita-tion Non-volatile component 57 62 59 63 58 60 65 50 of paint (% byweight) Intermediate coating performance Gloss (60°) 96 90 92 89 90 9390 93 Hardness F H HB F HB HB F H Xylene rubbing A A A A A A A AComposite paint film performance Chipping resistance B A A A B D A D*Pigment precipitation was observed.Viscosity Variation of Aqueous Paints: Sufficient ion exchange water wasadded to the aqueous paint to produce a Ford cup No. 4 viscosity of 50seconds (20° C.), and the aqueous paint was then stored for 10 days at40° C. The viscosity of the aqueous paint following storage was measuredusing a Ford cup No. 4, and the variation in the viscosity valuerelative to the viscosity prior to storage was determined.Procedure for Evaluating Physical Properties of the Aqueous Paints

Gloss: The 60 degree gloss value (the 60 degree specular reflectance: %)was measured using a Handy Gloss Meter manufactured by Suga TestInstruments Co., Ltd.

Hardness: Hardness tests were conducted in accordance with the pencilscratch test of JIS K 5400, and the hardness symbol of the hardestpencil for which no scratching of the paint film occurred was recorded.

Xylene Rubbing: A flannel cloth was immersed in xylene, the cloth wasrubbed 50 times back and forth across the paint film using a rubbingtester, and the state of the paint surface was inspected visually, andevaluated in the manner described below.

-   -   A: No swelling or scratches    -   B: Slight scratching, with fine scratches visible    -   D: Marked swelling, and scratches visible

Chipping Resistance: Using a Gravelometer manufactured by Suga TestInstruments Co., Ltd., in an atmosphere at −20° C., 50 g of No. 7 gravelwas ejected at 0.4 MPa, and the degree of paint film separation uponcollision with the surface of the paint film was evaluated visually inthe manner described below.

-   -   A: Excellent (absolutely no separation)    -   B: Good (very slight separation observed)    -   C: Fair (some separation visible)    -   D: Poor (separation noticeable)

1. An aqueous resin composition comprising a polyester resin (A) havingan acid value within a range from 10 to 50 and a hydroxyl value within arange from 20 to 150, a vinyl modified polyester resin (B) having anacid value within a range from 20 to 100 and a hydroxyl value within arange from 20 to 150, and a curing agent (C), wherein said polyesterresin (A) comprises structural units provided by an aromatic acid andfrom an alicyclic acid, and a combined total of said structural unitsprovided by said aromatic acid and said alicyclic acid accounts for atleast 70 mol % of all structural units provided by polybasic acids insaid polyester resin (A), and said vinyl modified polyester resin (B)comprises an aliphatic acid chain having a bonded vinyl polymer section,in which from 15 to 45% by weight of said vinyl modified polyester resin(B) is said vinyl polymer section, and from 10 to 50% by weight of saidvinyl polymer section is structural units provided by an α,β-ethylenebased unsaturated monomer having a carboxyl group wherein said vinylmodified polyester resin (B) is produced by condensing a vinyl modifiedfatty acid (D) containing a vinyl polymer section comprising a carboxylgroup, and a polyester resin (E) containing hydroxyl groups.
 2. Anaqueous resin composition according to claim 1, wherein said vinylmodified polyester resin (B) is produced by condensing a vinyl modifiedfatty acid (D) containing a vinyl polymer section comprising a carboxylgroup and an aryl group, and a polyester resin (E) containing hydroxylgroups.
 3. An aqueous resin composition according to claim 1, wherein amolar ratio within said polyester resin (A) between structural unitsderived from an aromatic acid and structural units derived from analicyclic acid is within a range from 20/80 to 50/50.
 4. An aqueouspaint comprising an aqueous resin composition according to claim 1.